Mac Excel Gantt Chart Builder

I need a straightforward, fully editable Gantt-style schedule built directly in an Excel workbook I can open on my Mac (Microsoft 365). The sheet should let me enter start and finish dates for each task and instantly display clean coloured bars across the timeline. My only must-have feature is the ability to switch the time scale—day, week, or month—without breaking the formatting or formulas. I do not require complex dependency calculations or progress tracking right now, but please structure the sheet so those elements could be added later.

Deliverables:
• Unlocked .xlsx file that works natively in Mac Excel
• Clear in-sheet instructions or a short read-me on how to add tasks and change the time scale
• Light, well-commented formulas (no VBA is fine, but if you choose macros keep them Mac-compatible)
• A quick test dataset so I can see the chart populate immediately

I’ll consider the project complete when I can duplicate rows, adjust the date range, toggle the scale, and see the Gantt bars update accurately without manual tweaks.